Electric toothbrushes and other small electrical appliances such as shaving apparatus, kitchen appliances, and the like generally have a watertight housing in the interior in which there are often switches. In some cases, it may be desired that the actuating energy for such switches be passed through the housing wall in a manner preventing the ingress of water. In a typical arrangement the switch or other mechanism (e.g., a brake, coupling, valve, transmission, etc.) to be actuated lies behind an aperture in the housing wall which is sealed by an elastic membrane. To activate the appliance, the user presses (e.g., presses with his or her finger) on the membrane, thereby actuating the switch or other mechanism underneath. The membrane is generally made of a soft plastic material which is bonded to the hard plastic housing wall. The membrane and the housing wall can be injection-molded by a two-component injection method.
As a visual and tactile indicator to the underlying switch, the membrane often has a projection or some other three-dimensional structure on its outside surface. In cases in which the three-dimensional structure is made of the same material as the membrane, the three-dimensional structure and the membrane generally have the same color, which can impair recognition of the three-dimensional structure.
For this reason, some known appliances include a metal actuating button inserted in a hole passing through the membrane. However, such an arrangement can allow liquid (e.g., water) to pass through the hole into the interior of the housing. Thus, water-tightness of the housing may no longer be assured.